The present invention relates to a method of developing and treating a PS plate and an apparatus for practicing the method.
A PS plate on which the image of an original has been printed is ordinarily developed and treated by applying a development treatment liquid (hereinafter referred to merely as "a treatment liquid") and then rubbing the plate with brushes or a sponge while conveying the plate through a developing bath. Since no photosetting occurs in the non-image portions of the PS plate, that is, regions in which no image of the original has been printed, the non-image portions are changed into a swelling film by the treatment liquid containing organic solvents or alkali aqueous solutions in the aforementioned development treatment. The swelling film or the non-image portions, can be readily removed by a rubbing device such as a brush or sponge as a result of which only the image portion remains on the PS plate. As a result, dissolved materials such as photosensitive materials from the PS plate are mixed into the treatment liquid. Furthermore, as the treatment liquid is in general applied in a shower system to the PS plate passing through the developing bath, the plate tends to deteriorate because of its contact with air. For instance, its pH tends to be lowered by the presence of carbon dioxide gas dissolved therein.
Because of this phenomenon, the developing ability of the treatment liquid generally decreases in proportion to the amount of treatment of the PS plate and the lapse of time. When the developing ability of the treatment liquid has decreased to its minimum acceptable limits, then it is necessary to replace the treatment liquid. If a PS plate is treated with treatment liquid of which the developing ability has been decreased beyond its acceptable limits, then the photosensitive film in the non-image portion tends to remain on the surface of the PS plate thereby making the resultant prints unclear or dirty and making it difficult to reproduce the image of the original satisfactorily, for instance, with a satisfactory tone.
Heretofore, the treatment of a PS plate in general included a developing process, a washing process, a gum coating process and a drying process. However, recently a washing-less treatment system in which the washing process is eliminated and the PS plates delivered from the developing process directly to the gum coating process has been employed to eliminate a public hazard due to the waste water discharged during the washing process. However, the washing-less treatment system is still disadvantageous in the following points. Even if treatment liquid whose treatment ability is near the lower limit yet within the acceptable range is used to treat the PS plate, the background of the PS plate may still be made dirty and the inking may be unsatisfactory. In addition, the treatment liquid into which the photosensitive material has been dissolved, namely the deteriorated treatment liquid, tends to stick onto the surface of the PS plate, and mix with the gum liquid again making the background of the PS plate dirty and causing unsatisfactory inking.
Accordingly, in the washing-less treatment system it is essential to suitably design a pair of rollers provided at the output side of the developing process section to squeeze off the treatment liquid on the PS plate to avoid as much as possible introduction of the treatment liquid into the gum coating process. It is impossible to completely eliminate the introduction of the treatment liquid into the gum coating process. This problem may however be solved by replacing the treatment liquid before the amount of photosensitive material dissolved in the treatment liquid reaches a high level. However, this solution is not economical.
An object of the present invention therefore is to provide a method for developing and treating a PS plate in which the development treatment is accomplished under the condition that the amount of photosensitive material dissolved in the treatment liquid is reduced but in which the treatment liquid can be used economically and to provide an apparatus for practicing the method.